`useEffect($callback, $deps)` where {
    $callback <: contains `fetch`,
    register_diagnostic(
        span = $callback,
        message = "Don't fetch inside useEffect. Use TanStack Query instead.",
        severity = "error"
    )
}

{
  "plugins": ["./rules/no-use-effect-fetch.grit"]
}

`pattern_to_match` where {
    register_diagnostic(
        span = $matched_var,
        message = "Your message here",
        severity = "error"  // hint | info | warn | error
    )
}

`console.log($args)` where {
    register_diagnostic(
        span = $args,
        message = "Remove console.log before committing",
        severity = "warn"
    )
}

`useMemo($args)` where {
    register_diagnostic(
        span = $args,
        message = "useMemo unnecessary with React Compiler. Remove it.",
        severity = "warn"
    )
}

`await import($path)` where {
    register_diagnostic(
        span = $path,
        message = "Use static imports at the top of the file",
        severity = "error"
    )
}

`useState($initial)` where {
    not $initial <: contains `atom`,
    register_diagnostic(
        span = $initial,
        message = "Prefer Jotai atoms over useState for shared state",
        severity = "info"
    )
}

language css;

`$selector { $props }` where {
    $props <: contains `color: $color` as $rule,
    not $selector <: r"\.color-.*",
    register_diagnostic(
        span = $rule,
        message = "Use .color-* utility classes instead of explicit colors"
    )
}

project/
├── biome.json
└── rules/
    ├── no-console-log.grit
    ├── no-use-memo.grit
    ├── no-use-callback.grit
    ├── no-dynamic-import.grit
    └── no-fetch-in-effect.grit

{
  "$schema": "https://biomejs.dev/schemas/2.0.0/schema.json",
  "plugins": [
    "./rules/no-console-log.grit",
    "./rules/no-use-memo.grit",
    "./rules/no-use-callback.grit"
  ],
  "linter": {
    "enabled": true
  }
}